Suspended ferric oxyhydroxides

The Eh and pH of iron-rich natural waters, most of which contain suspended ferric oxyhydroxides, places these waters on the ferric or ferrous species-ferric oxyhydroxide boundary. Acid-mine discharges usually have pHs between 2 and 5 and Ehs from within the Fe3+ field down to zero volts. Iron-rich ground waters are usually on the same boundary, with pHs between 5 and 8 and Ehs from +0.3 to —0.1 volt. 

Erior to analysis. Although some suspended ferric oxyhydroxides could ave been present and have passed through the filter paper, the amount of such material must have been negligible for purposes of this study in that pQ values calculated using the mFe (total) analyses were identical to such values calculated from mFe (II) concentrations measured in the same samples. Analyzed ferrous iron values are probably accurate to 0.5% total dissolved iron values to 1%. 

Suspended Ferric Oxyhydroxides in Some Ground Waters... 

Figure 10.16 Adsorption of uranyl onto suspended ferrihydrite 1.00 g/L as Fe or 1.79 x 10 M as Fe) at 25°C as a function of pH in C02-free 0.1 M NaN03 solutions. The ZPC of the oxyhydroxide is at pH 7.9. Ferrihydrite total surface area is 306.4 m /L. Total uranium is 10" M (2.38 mg/L). Reprinted from Geochim. et Cosmochim. Acta, 49(18), C. K. D. Hsi and D. Langmuir, Adsorption of uranyl onto ferric oxyhdroxides Applications of the surface complexation site binding model, pp. 2423-2432, Copyright 1985, with permission from Elsevier Science Ltd., TTie Boulevaid, Langford Lane, Kidlington 0X5 1GB, U.K.

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